1. Field of the Invention
The present invention relates to a process for producing halogenated phenol compounds. In particular, the present invention relates to a process for producing halogenated phenol compounds from phenol compounds in the presence of a halide ion (X.sup.-) and a semiconductor catalyst with a photocatalytic activity under light irradiation conditions.
2. Description of the Prior Art
A halogenated phenol compound is used e.g. as an active ingredient in medicines and agrochemicals or as a synthetic intermediate of such an active ingredient. For example, a phenol compound containing a radioactive halogen atom in the molecule is widely used as a radioactive tracer used for measurement of the in vivo movement or functions of pharmaceutical chemicals etc., or as an active ingredient in diagnostic or therapeutic drug. Specifically, thyroxine containing iodine-125, for example, is used for measurement of thyroid functions; an antihuman colon cancer-derived sugar chain antigen antibody iodinated with iodine-125 is used for diagnosis of the cancer of digestive organs; an antihuman prostate acid phosphatase antibody iodinated with iodine-125 is used for diagnosis of prostate cancer; and human fibrinogen iodinated with iodine-125 is used for detection of thrombus sites.
In general, since a radioactive halogen atom is supplied stably in the state of a halide ion, a method of reacting the halide ion (X.sup.-) with a phenol compound in the presence of an oxidizing agent such as chloramine T (N-chloro-4-methylbenzenesulfonamide sodium salt), Iodo-Gen.TM. (1,3,4,6-tetrachloro-3 .alpha., 6 .alpha.-diphenylglycoluril), Iodo-beads.TM. (N-chloro-benzenesulfonamide (sodium salt) derivatized, uniform, nonporous, polystyrene beads) and hydrogen peroxide is used for producing the above-described phenol compound containing a radioactive halogen atom in the molecule.
In the method described above, however, the phenol compound to be halogenated is placed under oxidizing conditions, thus making it difficult to apply said method to those compounds which are unstable under such conditions.
Accordingly, there is a demand for development of a method of halogenation under moderate conditions applicable to those phenol compounds which are unstable under oxidizing conditions.